Handover mechanisms in next generation heterogeneous wireless ...

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DYNAMIC NEIGHBOUR TRUST INFORMATION RETRIEVAL FOR GLOBAL ROAMING LU REQ LU REPL PSM REQ PSM REPL CLU CPSM rol beacon TBI TLI beacon beacon Ttx - 68 - TNUI Rn LU REQ LU REPL CLU Figure 4.6 The power save mode NTC procedure According to the PSMN procedure shown in Figure 4.6, theoretically, the NUI interval should be as short as possible to maintain a high degree of accuracy of neighbouring relationship between two networks. However, practically, the frequency of the related LU has to be balanced against the signalling overheads and the power consumption of a mobile terminal. The maximum NUI is explained as follows. In the worst case, a mobile user has to renew its oPOA location as its residence time at the oPOA has just elapsed at time A as shown in Figure 4.6. To get an accurate picture of the neighbouring relationship between the oPOA and nPOA, the mobile user has to perform another location update through the nPOA before time B. It is assumed that the radio coverage of the two POAs is partially overlapped. In a handover, overlapped radio coverage may have the effect of probable decrease of a mobile user’s residence time on a network. The variation in residence time caused by radio overlap effect is denoted as t ol , which fluctuates according to an exponential probability distribution with the mean of u . T �� R � r �C �C (Equation 4.7) nui n ol LU PSM
DYNAMIC NEIGHBOUR TRUST INFORMATION RETRIEVAL FOR GLOBAL ROAMING where R n represents the maximum residence time of the mobile user in the nPOA without handover. The location update cost and the power save mode registration cost largely depend on the signalling process taking place in networks. The NTC update interval may change over different access networks. Taking different approaches, the PSMN and AOMN methods are intended to complement each other in facilitating network trust information distribution among neighbouring networks. The AOMN that relies on actual handover event can produce the most accurate information about neighbouring relationship. In the AOMN, the mobile users sacrifice their QoS and have the attached network obtain its neighbour network trust pattern in return. In contrast, the PSMN derives neighbouring relationship from analysing location update records. The mobile users selected for participating in the PSMN sacrifice their power consumption instead. 4.5 Performance Evaluation A random walk model [78] as shown in Figure 4.7 is introduced to simulate a multioperator environment. It is assumed that the radio coverage of every network (denoted as a cell in the model) is hexagonal shaped, and has six neighbouring cells. A mobile user has equal probability of moving to any of the six neighbouring networks. The cell residence time follows a Gamma distribution. The rings as marked in Figure 4.7 are used to group cells. Each ring of cells is surrounded by the neighbouring outer ring of cells, and is also adjacent to an inner ring of cells. The outmost ring of cells is referred to as boundary ring or Ring n, and assumed to be in an absorbing state. A mobile user entering the boundary ring will remain in that ring at all times. This can be explained by the nomadic behaviour of a mobile user. Moreover, it is assumed that each network belongs to an independent operator to make the handover task more challenging. Thus, whenever a mobile user leaves a cell, a NTC exchange between two adjacent cells along with a handover can be expected. The objective of the proposed NTC process is to have every network to obtain its neighbour network trust pattern. According to the procedure of Figure 4.4, this requires that a network has to exchange the NTC data with all of its 6 neighbouring networks at least once. - 69 -
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Handover Mechanisms in Next Generat
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ACKNOWLEDGMENT First of all, I woul
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TABLE OF CONTENTS 4.4.2 Power Save
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LIST OF FIGURES LIST OF FIGURES Fig
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LIST OF FIGURES Figure 7.2 A generi
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ABSTRACT New access technologies su
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Chapter 1 INTRODUCTION New access t
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INTRODUCTION becomes available. Han
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INTRODUCTION The above multipliciti
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INTRODUCTION network trust pattern
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INTRODUCTION 1.3 Related Publicatio
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INTRODUCTION TECHNICAL REPORTS XIII
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HANDOVER MANAGEMENT horizontally. H
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HANDOVER MANAGEMENT The objective o
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Page 31 and 32: HANDOVER MANAGEMENT proposed archit
Page 33 and 34: HANDOVER MANAGEMENT Access point (A
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Page 39 and 40: HANDOVER MANAGEMENT The two schemes
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Page 43 and 44: 3.1 Introduction Chapter 3 HANDOVER
Page 45 and 46: SECURITY FOR HANDOVER ACROSS HETERO
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Page 93 and 94: Chapter 5 TRUST ASSISTED HANDOVER A
Page 95 and 96: TRUST ASSISTED HANDOVER ALGORITHM F
Page 123 and 124: Chapter 6 PROXY BASED AUTHENTICATIO
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PROXY BASED AUTHENTICATION LOCALISA
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MULTI-INTERFACE MOBILE MODEL FOR ME
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CONCLUSIONS AND FUTURE RESEARCH WOR
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ABBREVIATIONS 3G 3rd Generation Wir
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ABBREVIATIONS LS Location Server MH
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ABBREVIATIONS THOA Trust Assisted H
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REFERENCES [12] C. Politis, T. Oda,
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REFERENCES [37] Wi-Fi Alliance, "Wi
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REFERENCES presented at IEEE Intern
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REFERENCES [90] R. Verdone and A. Z
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REFERENCES [116] K. E. Malki and H.
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